Self-contained automatic lash adjuster



Oct. 8, 1957 I c SAMPIETRQ 2,808,818

SELF-CONTAINED AUTOMATIC LASH ADJUSTER Filed June 27, 1955 r 2Sheets-Sheet l v Ach /[e5 dfiarles fiazz mlefz a 1957 7 A. c. SAMPIETRO2,808,818

SELF-CONTAINED AUTOMATIC LASH ADJUSTER Filed June 27, 1955 2Sheets-Sheet 2 EYE ZjZ ETT' 4 Advil/es Char/as Sampzzro. MZwwm, I %ZIHEUnited States Patent SELF-CONTAINED AUTOMATIC LASH ADJUSTER AchillesCharles Sampietro, Ann Arbor, Mich, assiguor to Thompson Products,-Inc., Cleveland, 01210, a corporation of Ohio Application June 27,1955, Serial No. 518,281

18 Claims. (Cl. 123-90) The present invention relates to a lash adjusterwhich will automatically compensate for slack in engine valve linkageand more particularly to a lash adjuster having self-contained thereinhydraulic fluid under pressure for taking up the slack and which doesnot add to the reciprocating weight or inertia of the linkage.

It is an object of this invention to provide an automatic lash adjusterwhich has self-contained therein hydraulic fluid under pressure andwhich thereby dispenses with the need for the use of connections to anoil gallery or the like. In this regard it should be noted that somevalve in head engines do not have a supply of oil or oil gallery inproximity to the valve linkage and that therefore this invention isparticularly useful with-such engine structures.

Another-object of this invention'is to provide an automatic lashadjuster which is economical to manufacture and assemble and which maybe readily applied to the post on which a rocker arm is pivotallymounted.

Yet another object of this invention is to provide an automatic lashadjuster which can have self-contained therein a hydraulic fluid suchfor illustrationas a heavy viscous fluid that is relatively stabledespite temperature variables. Excellent results may be attained by theuse of a fluid such for example as Silicone,- which ismethylpoly-siloxane.

In accordance with the general features of this invention, there isprovided in a valve gear including a push rod, a rocker arm actuated bythe rod, a spring loaded engine valve actuated by the arm, theimprovement of a mounting for the rocker arm accommodating rockingthereof by the push rod and the spring loaded valve, a lash adjuster onthe mounting effective to hold the rocker arm in contact with the pushrod and valve without interfering with proper seating of the valve andincluding a restricted orifice, the lash adjuster having self-containedtherein hydraulic fluid, and means for effecting flow of such fluidthrough the restricted orifice in the adjuster in response to slackconditions developed in the valve gear.

Another feature of this invention relates to the provision in theaforesaid adjuster means for affording a bleed for the fluid in additionto its flow through the main orifice in response to slack conditions ofthe valve gear.

Yet another feature of this invention relates to the provision in theaforesaid valve adjuster of a simple spring urged piston for impellingthe contained hydraulic fluid toward the rocker arm to hold the adjusterin hydraulically cushioned cooperation with the rocker arm.

ther objects and features of this invention will more fully appear fromthe following detailed description taken in connection with theaccompanying drawings, which illustrate several embodimentsthereof, andin which:

Figure 1 is a transverse cross-sectional view, with'parts in elevation,of a valve in head internal combustion engine Figure 3 is a fragmentarycross-sectional view corresponding to a portion of Fig. 1 showing thevalve means and the bleed passage and showing the valve ball in closingcooperation with the valve orifice;

Figure 4 is a fragmentary cross-sectional view' similar to Fig. 1 butillustrating a modification of the invention; and

Figure 5 is a fragmentarycross-sectional view similar to Fig. 1 butillustrating still a third form of the invention.

As'shown in the drawings: 1

In Fig. 1 there-is illustrated in fragmentary manner a valve in headtype of engine to which any one of the several forms of my valveadjuster may be adapted. The internal combustion engine 10 includes acylinder block 11 and a cylinder head 12. The head 12,has a guide 13receiving in slidable relation therein the stem 14 of a poppet valve 15.The head 16 of the valve 15 cooperates with "a seat 17 in the enginehead 12 to control the flow between the'valve port 18 in the head 12 andthe combustion chamber 19. The upper end of the valve stem has grooves20 therearound and the conventional split valve locks 21 have beadsseated in these grooves. A valve spring retainer 22 is fixedly held onthe upper end of the valve stem by'the locks 21 and a valve spring23-surrounding the "valve stem'has one end bottomed in the retainer 22and the other end bottomed on a shoulder 24 of the engine head 12surrounding the guide 13. The valve spring 23 is compressedto hold thevalve head 16 against its seat 17.

by an upturned peripheral flange 28 to provide a centrally bowl-shapedfinterior 29. On one side of the socket 26 in the arm, the bottom of thebowl is raised to provide an inverted socket 30for .the rounded end 31of the'push rod 32. The pushrod 31 can "rock in the socket 30 and an oilaperture 33 is provided through the socket30 to lubricate the end 31 ofthe push rod.

On the opposite side of the socket 26 the bowl-shaped bottom portion 29of 'the'rocker arm 25 is depressed at 34 .to provide a rounded exteriorfor rocking on the end 35 of the valve stem 14.

In accordance with the features of this invention, the rocker arm 25 isheld in cooperation with the valve stem 14 and the push rod 32 by anautomatic lash adjuster designated generally by the reference character36. The (Fig. -l) lash adjuster 36 is associated with a mounting stem 37suitably secured to a boss 38 on the engine head 12. This mounting stem37 includes an enlarged head'39 which may be integrally formed therewithand in reality comprises a part .of thelash-adjuster 36.

The head 39 of the stem 37 is snugly disposed within the interior of ahollow-cylindrical member 40 having a lower rounded or semi-sphericalend 41 disposed inthe socket 26 of the rocker arm 25. In this manner therocker arm 25 is universally socketed on the lower rounded end 41 of themember 40.

It will also be noted that the rounded end 41 of member 46) has anaperture 42 through which the stem 37 extends in close cooperationtherewith. Rubber-0 rings 43 and 44 may be disposed between the head 39and member 40 and between the stem 37 and the rounded end41respectively. A spring45 under compression is disposed in the lower end'ofmem'ber 40 between the head 39 and the rounded end-41. Thus thisspring 45 is disposed in :a lower fluid chamber '46 in member 40 whichchamber is separated from the upper fluid chamber 47 by the head 39.

Referringnow to Fig. v3, it will be perceived that the head 39 has acentral bore 48 which extends into the receiving area.

Disposed at the bottom of the plug 49 is a cup-like ball cage 51resiliently snapped into snug engagement withthe wall of the bore 48directly below the plug 49. This cage is slightly larger than a ballvalve 52 adapted to close off the flow of fluid through the orifice 59.The cage below the ball 52 has spaced apertures 53 through which fluidcan flow.

As shown in Fig. 3, the ball when in its uppermost position closes offthe lower end of the orifice or passageway 50 was to shut oil the flowof fluid from lower chamber 46 to upper chamber 47 in member 40. In thisrespect it should be observed that the stem 37 has diametrically opposedapertures 54 at right angles to the bore 48 so that the bore 48 is incommunication with the lower chamber 46.

In addition, the head 39 of stem 37 is provided with a restrictedpassageway or bleed 55 through which fluid can flow between chambers 47and 46.

Now referring back to Fig. 1, it will be perceived that the upper end ofthe hollow member 40 has disposed therein a spring urged closure in theform of a hollow piston 56 which when in its uppermost position abuts astop ring 57 in the upper part of member 40. The lower or head end ofthe piston 56 defines the top of the chamber 47 and is resiliently heldin engagement with the viscous fluid in chamber 47 by the compressionspring 58. Springs 58 and 45 together have a force less than thatexerted by the engine valve spring 23 so as to not interfere with theclosing of the valve head 16.

Access to the interior of the hollow member 40 may be easily attained byremoving the snap retainer ring 57 whereupon the spring 58 and thepiston 56 may be removed from the upper part of the member 40. Thispermits the introduction of fluid such as hydraulic fluid in the upperchamber 47. As noted before, it is contemplated that a heavy relativelytemperature stable fluid should be used. Excellent results have beenattained by the use of Silicone.

According to this invention, the rocker arm 25 univer sally moves asrequired about the rounded end 41 of the lash adjuster. Pressure in theupper chamber or reservoir 47 caused by the spring 58 insures filling ofthe lower chamber 46 forming a fluidlock. Then, too, spring 45 in thelower chamber 46 also insures that the'rocker arm 25 will be maintainedin proper cooperation with valve stem 14 and push rod 32. i

The ball check valve 52 can open to cause extension when the ball checkvalve 52 is closed, retraction can take place by leak down throughorifice or passageway 55. The retraction maybe otherwise; obtained byomitting the middle ring seal 43 or'bythe provision of a nick (notshown) in the sealing surface of the ball 52.

The upper chamber or reservoir, generally speaking, has three mainpurposes. One is to store a supply of fluid, to feed the lower chamber46 when necessary, and to accept the return of fluid at the time ofretraction. The lower chamber 46 defines a lock and has the principalfunction of holding position. It will be appreciated that adjustmentsmay be easily made by changing the pressure exerted by the lower spring45.

In Figure 4, there is disclosed a slightly dilferent form of lashadjuster 36' associated with the upper end of the fixedly mounted studor stem 37' for coaction with a socket in the rocker arm 25'.

In this formof the invention, as Well as in the form shown in Figure tobe hereinafter described, the rocker arm coacts with the valve linkageand push rod in the same manner as in the first form. Also, the lashadjuster, which'has self-containedtherein hydraulic fluid underpressure, coacts with the rocker arm to hold it in yieldable cooperationwith the upper ends of the valve stem and the push rod as in thepreferred form. For simplicity purposes, the valve linkage push rod andengine parts are not shown in Figures 4 and S, such parts being fullyillustrated, however, in Figure 1. The principal difference between thetwo modifications and the form shown in Figure 1 resides in theconstruction of the lash adjuster.

Referring again to Figure 4, it will be perceived that the stud or stem37 projects through the enlarged aperture 27' of the rocker arm 25 so asto permit pivoting of the rocker arm and extends through the centralbore 60 of a hollow cylindrical or tubular member 40'. This member 40'has a rounded or semi-spherical end 41 socketed in the rocker armandabout which the rocker arm universally pivots. A suitable 0 ring 61 isdisposed between the wall of bore 60 and the stem 37'.

The upper end of the tubular member 40 has an enlarged cylindricalrecess 62 in which is snugly fitted an enlarged head 63 integral withthe upper end of stem 37. An 0 ring 64 is disposed between the head 63and the wall of member 40'. A lower or oil lock chamber 65 is locatedbetween the underside of the head 63 and the lower portion of thetubular member 40'.

The upper portion of the head 63 is hollowed out to form an upper or oilpressure chamber 66 in which is disposed a spring urged piston 67between which on the wall of the head is an O ring 68. A compressionspring 69 bears on the upper end of the piston 67 and against a washer70 held in place by a snap ring 71 in the upper hollowed end of the head63.

The lower end of the head 63 comprises a barrier wall 72 separating thetwo chambers 65 and 66. This wall 72 is also provided with a bleed downpassage 73.

' The middle of wall 72 is apertured to receive a screw plug 74 defininga restricted orifice 75 leading into a ball valve receiving chamber 76in which is located a ball 77.

Coacting with the lower portion on the ball 77 is a compression spring78 tending to urge the ball upwardly into seated position on the lowerend of orifice 75. Lateral openings 79 are formed in the stud 37 andestablish a communication between the lower chamber 65 and the valveball chamber 76.

It will be appreciated that the chambers 65 and 66 may be filled withany suitable fluid although excellent results may be obtained by the useof a heavy viscous fluid such as silicone as previously described. Sucha fluid has a relatively flat viscosity curve with changes in atemperature.

Needless to say, the spring 69 of necessity must exert a pressure on thepiston 67 and the fluid which is not enough to overcome that of theengine valve spring such as spring 23 described in Figure 1, but enoughto insure that the semi-spherical fulcrum end 41 of the lash adjuster 36is maintaining rocker arm 25' in proper coaction with the valve stem andthe push rod.

The ball valve controlled passage 75 and the leakdown bleed cooperate toinsure respectively proper filling of chamber 65 and retraction of thehydraulic lash adjuster.

It is also contemplated that adequate hydraulic seals will beobtained bythe 0 rings 61 and 64 and that there will be little or no leakage forextended periods of operation. a a

The upper chamber or reservoir has three purposes: first, it hassufficient volume and spring actuation to keep the mechanism functioningafter a substantialamount of fluidis lost; second, it acceptsreturnfluid when the mechanism is over-extended and must retract; andthird, because it is pressurized for filling reasons, italso is thetakeup means for overcoming slack in the valve train and in'thelowerchamber or lock 65. g V

lt will be appreciated that otherwise the operation of this'modifiedlash adjuster 3 6 is quite similar to that of the first described form36.

In the modification shown in Figure 5, the rocker arm 25a, like thepreviously described rocker arms, is cooperable with the valve linkageand push rod and has an enlarged aperture 27a in its semi-sphericalsocket 26a through which extends the stem 37a secured in any suitablemanner to the engine block.

As in the other forms, the lash adjuster 36a includes a cylindricalhollow or tubular upstanding member 40a provided with a rounded orsemi-spherical lower end 41a which defines a universal fulcrum bearingagainst and on which the rocker arm 25a moves as in the previous forms.

The tubular member 46a is hollowed out to define lower and upper fluidor oil receiving chambers 80 and 81 separated by an intermediate barriermember 82 which is secured by a press fit to a sleeve 83 on the stem37a.

In the bottom of the lower chamber 80 is a rubber sealing ring 84 ofcupped or U-shaped cross section, the legs of which bear against thesleeve and the wall of the tubular member 40a. This U-shaped rubber ringcomprises a high pressure sealing cup.

The sleeve 83 carries a spring retaining collar 85 which, in turn,carries a one-way spring disk valve of the socalled Belleville type 86which will permit a one-way flow of fluid from the upper chamber 81 tothe lower chamber 80 through apertures 87 in the intermediate barrier82. While this barrier has a pressed fit on the sleeve 83 so as to bemovable therewith, it is loosely fitted in the tubular member 40a so asto allow leakdown of fluid between the barrier and the tubular member.

The one-way valve 86 is such as to enable a rapid filling of the highpressure or lower chamber 80 from the upper or loading chamber 81. Thisupper chamber 81 has a sealing ring or cup 88 in sealing position at theupper end of chamber 81 between sleeve 83 and the wall of tubular member400.

The rubber rin or cup 88 bears against a boss-like annular member 89between sleeve 83 and the wall of tubular member 40a and which isencircled by a frustoconical loading or compression spring 90. The lowerend of the spring 90 bears against the flange of boss member 89 and theupper end bears against an annular adjustment plate 91 on the sleeve inabutting relation with a snap ring 92 engaged in a groove 93 in thesleeve.

The upper end of stem 37a is threaded at 94 for receiving a nut 95 whichholds a cup-like dust cap 96 against the upper end of sleeve 83. Thiscap is telescoped over the upper portion of the tubular member 40a.

It will be noted that by removing the nut 95 the dust cap 96 and theparts in the upper portion of tubular member 40a, the chambers 81 and 80may be filled with suitable fluid such as oil or the like. Thus, thelash adjuster self contains its own hydraulic fluid.

The loading spring 90, as in the previous forms of the invention, has adownward force less than that 'exterted by the engine valve spring, suchas the spring 23 in Figure 1, so as not to interfere with the properclosing of the engine valve. However, it always exerts suflicientpressure through the hydraulic fluid to take up slack or lash as in theprevious forms. In other words, as in the previous forms the upperchamber 81 of oil constitutes a loading chamber and the lower chamber 80of oil con stitutes a lock which insures tight frictional bearing of thesemi-spherical end of tubular member 40a in the socket of the rocker arm25a.

It is believed that the operation of this third form of the inventionwill be otherwise apparent from the descriptions of the operation of thefirst two described forms.

I claim as my invention:

1. In a valve gear including a push rod, a rocker arm actuated by therod, a spring loaded engine valve actuated by the arm, the improvementof a mounting for the rocker arm accommodating rocking thereof by thepush rod and the spring loaded valve, a lash adjuster on said mountingincluding means effective tohold the rocker restricted orifice, saidlash adjuster having self-contained therein hydraulic fluid, and meansfor effecting flow of such fluid through said restricted orifice in theadjuster in'response to slack conditions developed in the valve gear.

2. In a'valve gear including a push rod, a rocker arm actuated by therod, a spring loaded engine valve actuated by the arm, the improvementof a mounting for the rocker arm accommodating rocking thereof by the'push rod and the spring loaded valve, a lash adjuster on said mountingincluding means effective to hold the rocker arm in contact with thepush rod and valve without interfering with proper seating of the valveand including a restricted orifice, said lash adjuster havingself-contained hydraulic fluid, means for effecting flow of such fluidthrough said restricted orifice in the adjuster in response to slackconditions developed in the valve gear, and means for affording a bleedforthe fluid in addition to the aforesaid flow through said orifice.

3. In a valve gear including a push rod, a rocker arm actuated by therod, a spring loaded engine valve actuated by the arm, the improvementof a mounting for the rocker arm accommodating rocking thereof by thepush rod and the spring loaded valve, a lash adjuster on said mountingincluding means effective to hold the rocker arm in contact with thepush rod and valve without interfering with proper seating of the valveand including a restricted orifice, said lash adjuster havingself-contained therein hydraulic fluid, and means for effecting flow ofsuch fluid through said restricted orifice in the adjuster in re sponseto slack conditions developed in the valve gear, said mounting includinga fixedly supported stem projecting upwardly from its support through anaperture in the rocker arm and said lash adjuster being associated withthe upper portion of said stem and 'socketed in said rocker arm foruniversal movement of said arm relative to said adjuster.

4. In a valve gear including a push rod, a rocker arm actuated by therod, a spring loaded engine valve actuatedby the arm, the improvement ofa mounting for the rocker arm accommodating rocking thereof by the pushrod and the spring loaded valve, a lash adjuster on said mountingincluding means effective to hold the rocker arm in contact with thepush rod and valve without interfering with proper seating of the valveand including a restricted orifice, said lash adjuster havingself-contained hydraulic fluid, means for effecting flow of such fluidthrough said restricted orifice in the adjuster in response to slackconditions developed in the valve gear, and means for affording a bleedfor the fluid in addition to its aforesaid flow through said orifice inresponse to other conditions in the adjuster, said mounting including afixedly supported stem projecting upwardly from its support through anaperture in the rocker arm and said lash adjuster being associated withthe upper portion of said stem and socketed in said rocker arm foruniversal movement of said arm relative thereto.

5. In a valve gear including a push rod, a rocker arm actuated by therod, a spring loaded engine valve actuated by the arm, the improvementof a mounting for the rocker arm accommodating rocking thereof by thepush rod and the spring loaded valve, a lash adjuster on said mountingincluding means effective to hold the rocker arm in contact with thepush rod and valve without interfering with proper seating of the valveand including a restricted orifice, said lash adjuster havingself-contained therein hydraulic fluid, means for effecting flow ofsuch, fluid through a restricted orifice in the adjuster in response toslack conditions developed in the valve gear, and means for affording-ableed for the fluid in addition to its aforesaid flow through saidorifice in response to other conditions in the adjuster, said floweffecting means asc sts toward the rocker arm to hold the adjuster incooperation with the rocker arm.

6. In a valve gear including a push rod, an apertured rocker armactuated by the rod, a spring loaded engine valve actuated by the arm,the improvement of a mounting for the rocker arm accommodating rockingthereof by the push rod and the spring loaded valve, a lash adjuster onsaid mounting having self-contained hydraulic fluid and effective tohold the rocker arm in contact with the push rod and valve withoutinterfering with proper hollow member dividing it into upper and lowerchambers in which said hydraulic fluid under pressure is enclosed, andcheck valve means at said head for controlling the flow of hydraulicfluid between the chambers in response to lash condition in the valvegearv 7. In a valve gear including a push rod, an apertured rocker armactuated by the rod, a spring loaded engine valve actuated by the arm,the improvement of a mounting for the rocker arm accommodating rockingthereof by the push rod and the spring loaded valve, 21 lash adjuster onsaid mounting having self-contained therein hydraulic fluid andeffective to hold the rocker arm in contact with the push rod and valvewithout interfering with proper seating of the valve, said adjusterincluding a cupped hollow member having an apertured rounded bottom endon which said rocker arm is universally socketed, said mountingincluding a stem in said cupped member projecting through the aperturein said rounded end thereof and downwardly through a larger aperture inthe portion of said rocker arm socketed on said end and being fixedlysupported therebelow, said stem having a head in said hollow memberdividing it into upper and lower chambers in which said hydraulic fluidis enclosed under pressure, check valve means at said head forcontrolling the flow of fluid between the chambers in response to lashcondition in the valve gear, and a spring urged piston in said chambersfor applying pressure through the fluid to said rounded end of saidcupped member for maintaining it in hydraulically cushioned bearingagainst said rocker'arm.

8. In a valve gear including a push rod, an apertured rocker armactuated by the rod, a spring loaded engine valve actuated by the arm,the improvement of a mounting for the rocker arm accommodating rockingthereof by the push rod and the spring loaded valve, a lash adjuster onsaid mounting having self-contained therein hydraulic fluid andeffective to hold the rocker arm in contact with the push rod and valvewithout interfering with proper seating of the valve, said adjusterincluding a cupped hollow member having an apertured rounded bottom endon which said rocker arm is universally socketed, said mountingincluding a stem in said cupped member projecting through the aperturein said rounded end thereof and downwardly through a larger aperture inthe portion of said rocker arm socketed on said end and being fixedlysupported therebelow, said stem having on its upper portion restrictiveorifice means for regulating flow of hydraulic fluid in said adjusterand in and against said bottom end of said cupped member and means insaid adjuster for applying pressure against said fluid in a directiontoward the rocker arm.

9. In a valve gear including a push rod, an apertured rocker armactuated by the rod, a spring loaded engine valve actuated by the arm,the improvement of a mounting for the rocker arm accommodating rockingthereof by the. push rod and the spring loaded valve, a lash ad- 8juste'r on' said-rnounting having self-contained therein hydraulic fluidand etfective to hold the rocker arm in contact with the push rod andvalve without interfering with proper seating of the valve, saidadjuster including a cupped hollow member having an apertured roundedbottom end on which said rocker arm is universally socketed, saidmounting including a stern in said cupped member projecting through theaperture in said rounded end thereof and downwardly through an aperturein the portion of said rocker arm socketed on said end and being fixedlysupported therebelow, said stem having on its upper portion restrictiveorifice means for regulating flow of hydraulic fluid in said adjusterand in and against said bottom end of said cupped member and means insaid adjuster for applying pressure against'said fluid in a directiontoward the rocker arm, said latter means including a spring urged pistonexerting at all times a pressure through the fluid in a direction tomaintain the rocker arm socketed on said rounded end but which pressureis less than the spring loading of said engine valve.

10. In a valve gear including a push rod, a rocker arm actuated by therod, a spring loaded engine valve actuated by the arm, the improvementof a mounting for the rocker arm accommodating rocking thereof by thepush rod and the spring loaded valve, a lash adjuster on said mountingincluding means effective to hold the rocker arrnin contact with thepush rod and valve without interfering with proper seating of the valveand including a restricted orifice, said lash adjuster havingselfcontained therein hydraulic fluid, and means for effecting fiow ofsuch fluid through said restricted orifice in the adjuster in responseto slack conditions developed in the valve gear, said latter meansincluding a spring urged piston at all times exerting pressure on thefluid in a direction to urge same toward the rocker arm mounting.

11. A lash adjuster for a rocker-operated valve of the type having afulcrum part and a stud part compris ing means forming axially oppositemotive surfaces on a movable member connected to one of said parts,means confining a body of liquid in which said movable member issubmerged and forming fluid chambers on opposite sides of said memberfor confining a volume of static fluid adjacent each correspondingmotive surface, whereupon movement of said member will unbalance thehydraulic equilibrium in said chambers, means forming a first enlargedpassageway between said chambers and having a normally closed checkvalve therein for intermittently transferring fluid between saidchambers as a function of the movement of said member, means forming asecond restricted passageway between said chambers for continuouslytransferring fluid at a restricted rate of flow between said chambers asa function of the pressure differential between said chambers, andcontinuously biased movable wall means for one of said chambers toadjust the volume of said chambers and to transmit a slack-eliminatingforce between the parts through said fluid.

12. A lash adjuster as defined in claim 11, said fulcrum part comprisinga cup-shaped member having a cylindrical recess formed therein, saidstud part having a piston head forming said movable member and dividingsaid cylindrical recess into said fluid chambers, and a spring-biasedwall means forming said movable wall means and closing the end of saidcylindrical recess.

13. A lash adjuster as defined in claim 11, said fulcrum part comprisinga cup-shaped member having a first cylindrical recess formed therein,said stud part comprising a piston having a second cylindrical recessformed therein, said piston received in said first cylindrical recessand forming together with said fulcrum part a first one of said fluidchambers, and said biased wall means closing said second cylindricalrecess to form the other of said fluid chambers.

, 14. A lash adjuster as defined in claim 11, said fulcrum partcomprising a cup-shaped member having a cylindrical recess, said studpart extending through said cylindrical recess and having a pistonportion extending radially outwardly thereof for dividing saidcylindrical recess into said fluid chambers, and said movable wall meanshaving a biasing spring engaged against said stud part and against saidwall means and being disposed to close the end of said cylindricalrecess in said fulcrum part.

15. The method of automatically adjusting lash in a rocker-operatedvalve which includes the steps of confining a static body of fluid onaxially opposite motive surfaces of a relatively movable part of a studand fulcrum assembly, hydraulically balancing said part to a state ofequilibrium at rest, unbalancing the fluid load on one of said motivesurfaces in response to movement of said part, substantiallyinstantaneously balancing said part by intermittently transferring fluidbetween said surfaces as a function of the load induced displacement ofsaid part, continuously balancing said part over an appreciable intervalof time in a selected direction in response to an hydraulic unbalancebetween the parts extending through a slack condition, and applying apredetermined continuous biasing force between said parts through thefluid.

16. The method of adjusting lash in a rocker-operated valve whichincludes the steps of submerging a movable piston between a relativelymovable fulcrum part and a stud part in a static body of fluid toprovide chambers of fluid on opposite sides of the piston,intermittently transferring liquid from one chamber to the other chamberunder load to maintain the chambers in fluid equilibrium in response torelative load-induced movements of the piston, continuously transferringa restricted flow of liquid from one chamber to the other chamber tomaintain the chambers in fluid equilibrium under slack conditions, andcontinuously transmitting a minimum bias between the parts through theliquid to take up the slack between the parts and to maintain whollyliquid the fluid in said chambers.

17. In a lash adjuster for a rocker-operated valve, fulcrum means havingan external fulcrum surface, means including said fulcrum means having afirst recess, a stud extending through said fulcrum surface, meansincluding said stud forming together with said fulcrum means a firstfluid chamber in said first recess, means including said stud forming asecond recess, spring-biased movable wall means in said second recessforming together with means including said stud a second fluid chamber,means forming a check valve-controlled passage between said first andsecond chambers to accommodate fluid flow in response to relativemovement of said stud and said fulcrum means under load conditions, andmeans forming a restricted passage between said first and secondchambers to accommodate fluid flow in response to relative movement ofsaid stud and fulcrum means under slack conditions, said spring-biasedmovable wall means providing a continuous bias to keep the rocker andvalve in contact with one another and acting through the fluid.

18. In a lash adjuster for a rocker-operated valve, a relatively movablestud part and fulcrum part, one of said parts having a piston formedwith axially spaced pressure faces, self-contained hydraulic adjustmentmeans for said parts comprising means including said parts confiningsaid piston in a body of liquid thereby forming a fluid chamber onopposite sides of said piston, means forming a first passage tosubstantially instantaneously transfer fluid between said chambers inresponse to a load-induced relative movement of said piston, a checkvalve in control of said first passage to maintain said fluid chambersin fluid equilibrium as a function of said movement, means forming asecond passage and having a restriction formed therein to continuouslytransfer fluid at a restricted rate of flow between said chambers,thereby tending to maintain said chambers in fluid equilibrium when theparts are under slack conditions, movable wall means for one of saidchambers, and continuous biasing means engaged between said movable wallmeans and one of said parts to transmit a minimum slack-eliminatingforce between the parts through said liquid.

References Cited in the file of this patent UNITED STATES PATENTS 1,931,476

